The present invention is directed to process tomography and, in particular, to an electrical capacitance volume tomography (ECVT) system and using an adaptive capacitance sensor that allows focusing of the imaging region, increasing of volume image resolution, and steering of the electric field direction toward the region of interest.
Dynamic ECVT is a technology that senses measured capacitances between a sensor region to generate a whole volume image of the region. ECVT technology has been applied in providing imaging of objects moving through a pipe for example. ECVT has provided insights into multiphase flow phenomena in many industrial processes often in a combination of gas, liquid, and solid states, including pneumatic conveying, oil pipe lines, fluidized beds, bubble columns and many other chemical and biochemical processes. It may also be used for imaging biological processes and tissues.
An ECVT system is generally made up of a sensor, sensor electronics and a computer system for reconstruction of the image sensed by the sensor. An ECVT sensor is generally comprised of n electrodes or plates placed around a region of interest, in one embodiment providing n(n−1)/2 independent mutual capacitance measurements which are used for image reconstruction. Image reconstruction is performed by collecting capacitance data from the electrodes placed around the wall outside the vessel.
Further details regarding the theory and application of ECVT, sensor design, image reconstruction, and deployment of an ECVT system are found in the U.S. Patent Application Publication No. U.S. 2010/0097374 (U.S. patent application Ser. No. 11/909,548), the relevant disclosures of which are included by reference thereto as if fully set forth herein.
The present invention addresses resolution issues present with traditional ECVT technology. More particularly, the present invention addresses various factors that limit ECVT resolution, including:                The limited number of capacitance plates, and arrangements thereof, that can be used;        Limited sensitivity matrix produced from an uneven distribution of electric field intensity between different plate combinations;        Ill-conditioned system that makes the system more sensitive to noise at sections of the imaging domain compared to others;        Soft field nature of ECVT that is a consequence of the electric field changing its distribution inside the imaging domain based on change of material distribution; and        the inability to focus the sensors to a particular region of the imaging domain to allow for more focused reconstructed imaging;        the ill-posed inverse problem inherit in ECVT, which is a result of attempting to reconstruct a number of voxels that is much higher than measured data (i.e., less independent equations with more unknowns);        the limited number of independent capacitance measurements used to reconstruct a volume image;        the minimum required capacitance plate size that restricts scale of region being imaged;        the limited length of capacitance sensor restricted by maximum distance between plates and minimum size of each plate in an ECVT sensor;        the lack of flexibility in applying different voltage signals simultaneously to address different imaging applications.        
The present invention is based on an adaptive capacitor sensor array, and associated sensor electronic circuit, that allows focusing of the imaging region and the steering of the electric field direction toward the region of interest. It also allows for higher imaging resolution, increased number of independent capacitance measurements, and relaxation of sensor size limitations.